Semi-polar (11-22) GaN epitaxial films with significantly reduced defect densities grown on m-plane sapphire using a sequence of two in situ SiNx interlayers

This letter reports an approach for growing semipolar (11-22) GaN films with significantly reduced defect densities on m-plane sapphire substrates by incorporating a sequence of two in situ SiNx layers. The first SiNx layer is deposited on an initial epitaxial GaN layer and acts as a nanomask for preventing the propagation of extended defects. The second SiNx layer is deposited just after subsequent epitaxial GaN over-growth begins to form self-organized GaN islands, which encourages further GaN growth to initiate from the exposed island sidewalls while blocking the penetration of the remaining defects. X-ray rocking curve measurements show that our semipolar GaN films provide relatively low full width at half maximum values at 0.119 degrees along both the [11-23] and [10-10] directions. Additionally, transmission electron microscopy analyses confirm that our semipolar GaN films provide a significantly reduced density of threading dislocations down to similar to 6 x 10(8) cm(-2), which is two orders of magnitude less than those of conventionally deposited films.